This invention relates to combustion apparatus such as furnaces and boilers, and in particular to fluidized-bed combustion apparatus in which combustion takes place in a bed of noncombustible solid particles while the same is being "fluidized" or made to behave in a fluid-like manner by rising streams of air. More particularly, the invention pertains to a method of, and means for, introducing a fuel into the fluidized bed of such combustion apparatus.
In a fluidized-bed furnace for the incineration of sewage sludges and heat-producing industrial wastes such as pitch, sludge, and waste oil, for example, the fuel to be burnt is fed into the fluidized bed, as of quartz sand or pulverized limestone, from burners of various constructions and arrangements. The fuel may be either the heat-producing waste itself, heavy oil, light oil, finely divided coal or coke, natural or manufactured gas, or coal/oil mixtures among other materials.
An example of burners heretofore employed for the above purpose is the gun burner, which sprays a liquid fuel into the fluidized bed for diffusion combustion. The gun burner has the drawback of readily overheating, resulting in the thermal cracking of the fuel and in the consequent accumulation of carbon to the point of clogging up the burner nozzle. The noted problem is absent from another known burner which atomizes the injected fuel by high pressure air. This and other similar prior art burners, however, aim mostly at successful introduction of the fuel into the fluidized bed, rather than at the most efficient combustion in the fluidized bed.